Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$39.98	12.454%	$44.9591	$44.96	$44.95	$45.00
Purchase #2	$115.92	6.372%	$123.3064	$123.31	$123.30	$123.30
Purchase #3	$246.49	6.762%	$263.1577	$263.16	$263.15	$263.20
Purchase #4	$103.91	5.434%	$109.5565	$109.56	$109.55	$109.60
Purchase #5	$182.75	9.536%	$200.177	$200.18	$200.20	$200.20
Purchase #6	$87.57	6.739%	$93.4713	$93.47	$93.45	$93.50
Purchase #7	$56.25	5.810%	$59.5181	$59.52	$59.50	$59.50
7 purchase totals =	$832.87		$894.1461	$894.16	$894.10	$894.30